I found a +2 bonus titan break and at first I thought that it might increase the likelihood of a successful block, dodge or parry triggering a break but I don't believe that this is the case. Since equipping it, I've noticed that the size of the hit window for each break is higher than it used to be, sometimes as many as 8 hits, which leads me to believe that this style of gem increases the hit window of breaks by the number indicated on the gem. I don't have any empirical evidence to support this, it's just my observations for now.